Prerequisites for revitalization of a landscape damaged by floods
2000
Janecek, M. (Vyzkumny Ustav Melioraci a Ochrany Pudy, Praha (Czech Republic))
The runoff from a catchment is primarily determined by the amount of precipiation, the rate of water infiltration into soil, the soil moisture storage, the vegetation cover, the presence of impermeable areas, the surface retention, the size of catchment, its slope, etc. In particular, the effect of soil, its surface and cover on the retention and runoff of water in a small catchment where the land is prevailingly used for agriculture can be illustrated by using the so-called runoff curve number (CN) method. With the runoff curve number method, one can estimate explicitly the effect of the hydrological characteristics of a catchment on an amount of runoff caused by a certain daily precipitation sum. In this paper, a comparative analysis is made using two typical values of the 24-hour precipitation sum, namely, 40 and 100 mm. The former value is relatively low and appears, in our conditions, with a return period of 2 to 3 years while the after is relatively high and re-appears on most sites once a hundred years or more. The volumes of runoff caused by either of the said two daily precipitation sums under different catchment conditions are used to quantify the runoff potential of two extreme agricultural land use types, fallow and permanent grassland. In addition, the same methodology has allowed estimating the effect (in terms of surface runoff) of various erosion control measures applied in the field crop production. It becomes obvious that, after high precipitation, large amounts of surface runoff occur. Therefore, this runoff has to be safely disposed of either by providing a sufficient flow capacity of surface streams and drains or by exploiting the retention capacity of inundation areas (except for the locations of valuable assets which have to be protected). It is suggested that the natural extent of the inundation areas in the landscape is demarcated by the presence of fluvisols
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